Each Server Message Block (SMB) session consumes server resources. Establishing numerous null sessions will cause the server to slow down or possibly fail. A malicious user might repeatedly establish SMB sessions until the server stops responding; at this point, SMB services will become slow or unresponsive.

The Microsoft network server: Amount of idle time required before suspending session policy setting determines the amount of continuous idle time that must pass in an SMB session before the session is suspended due to inactivity. You can use this policy setting to control when a computer suspends an inactive SMB session. The session is automatically reestablished when client computer activity resumes.

For this policy setting, a value of 0 means to disconnect an idle session as quickly as is reasonably possible. The maximum value is 99999, which is 208 days. In effect, this value disables the policy.

Each SMB session consumes server resources, and numerous null sessions slow the server or possibly cause it to fail. An attacker could repeatedly establish SMB sessions until the server's SMB services become slow or unresponsive.